1. Technical Field
The present invention relates to a method for manufacturing a light emitting device comprising a light emitting element and an optical part.
2. Background Art
A light emitting diode (LED) using a nitride semiconductor has been widely known. A sapphire substrate is often used as a growth substrate for the nitride semiconductor. The nitride semiconductor and the sapphire substrate constitute alight emitting element of a light emitting device. The nitride semiconductor and the sapphire substrate are generally made of a material with a higher refractive index than that of the outside thereof. In this regard, the use of the higher-refractive-index material in the light emitting element tends to cause a light to be trapped within the light emitting element when extracting the light from the light emitting device. This is due to a decreased critical angle of a total reflection at an interface between “light emitting element composed of the nitride semiconductor and the sapphire substrate” and the outside thereof. The trapped light also tends to be reflected many times within the light emitting element while being absorbed in a metal part of the light emitting device (e.g., an electrode for the light emitting element), which leads to an attenuation of the light.
For example, the light emitting device disclosed in WO 2011/152262 (Patent Literature 1) has a decreased number of the light reflection within the light emitting element so that an improved light-extraction efficiency is provided. The disclosed light emitting device has a light-permeable substrate, which has been bonded thereto, to substantially increase the thickness of the light emitting element.
While on the other hand, there is another light emitting device having a phosphor for emitting a desired light therefrom. For example in the light emitting device disclosed in WO 2011/126000 (Patent Literature 2), “light emitting element for emitting blue light” and “phosphor for absorbing blue light and then emitting yellow light as a complementary color of the blue” are in a bonded state with each other. This light emitting device is capable of emitting a while light due to a mixing effect of the blue light from the light emitting element and the yellow light from the phosphor.    See Patent Literature 1: WO2011/152262    See Patent Literature 2: WO2011/126000    See Patent Literature 3: JP2010-46696    See Non-Patent Literature 1: Hideki Takagi, “Wafer Direct Bonding Technique”, online, National Institute of Advanced Industrial Science and Technology, [Search on 31 Jan. 2013], Internet (URL:http://staff.aist.go.jp/takagi.hideki/waferbonding.html)